Warning: file_get_contents(/data/phpspider/zhask/data//catemap/8/mysql/58.json): failed to open stream: No such file or directory in /data/phpspider/zhask/libs/function.php on line 167

Warning: Invalid argument supplied for foreach() in /data/phpspider/zhask/libs/tag.function.php on line 1116

Notice: Undefined index: in /data/phpspider/zhask/libs/function.php on line 180

Warning: array_chunk() expects parameter 1 to be array, null given in /data/phpspider/zhask/libs/function.php on line 181

Warning: file_get_contents(/data/phpspider/zhask/data//catemap/0/xml/14.json): failed to open stream: No such file or directory in /data/phpspider/zhask/libs/function.php on line 167

Warning: Invalid argument supplied for foreach() in /data/phpspider/zhask/libs/tag.function.php on line 1116

Notice: Undefined index: in /data/phpspider/zhask/libs/function.php on line 180

Warning: array_chunk() expects parameter 1 to be array, null given in /data/phpspider/zhask/libs/function.php on line 181
Java–;MySQL连接获取程序_Java_Mysql_Database Connection_Getter - Fatal编程技术网

Java–;MySQL连接获取程序

Java–;MySQL连接获取程序,java,mysql,database-connection,getter,Java,Mysql,Database Connection,Getter,我需要将我的连接发送到CarDAO类。我为此创建了getMyConn getter,但它键入“myConn无法解析为变量”。我怎样才能为它创建getter呢 public class ConnectionDB { public ConnectionDB() { String dbHost="localhost"; String dbDatabase="cars"; String dbUser = "root"; Strin

我需要将我的连接发送到CarDAO类。我为此创建了getMyConn getter,但它键入“myConn无法解析为变量”。我怎样才能为它创建getter呢

public class ConnectionDB {
    public ConnectionDB() {

        String dbHost="localhost";
        String dbDatabase="cars";
        String dbUser = "root";
        String dbPassword = "";
        String connectionUrl = "jdbc:mysql://" + dbHost
                + "/" + dbDatabase
                + "?user=" + dbUser
                + "&password=" + dbPassword;
        try{
        // 1. Get a connection do database
        Connection myConn = DriverManager.getConnection(connectionUrl);
        // 2. Create a statement
        Statement myStmt = myConn.createStatement();
        // 3. Execute SQL query
        String sql = "";
        //int rowsAffected = myStmt.executeUpdate(sql);
        //System.out.println("Rows affected " + rowsAffected);
        // 4. Process the result set
        }
        catch(Exception exc) {
            exc.printStackTrace();
        }
    }
    public Connection getMyConn(){
        return myConn;
    }
}

只需将myConn置于构造函数外部,使其成为对象的属性

 Connection myConn;
然后,在构造函数中

try{
    // 1. Get a connection do database
    myConn = DriverManager.getConnection(connectionUrl);
    // 2. Create a statement
    Statement myStmt = myConn.createStatement();
    // 3. Execute SQL query
    String sql = "";
    //int rowsAffected = myStmt.executeUpdate(sql);
    //System.out.println("Rows affected " + rowsAffected);
    // 4. Process the result set
}

此外,不建议在构造函数中初始化连接。您可以在需要时使用单例类来获取连接。

在哪一行获得此错误?